Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries
You are correct sir
.
Basically, what you need are these things:
- How hard would you like to run your XM-L? I'm guessing around 3.0A
- What is the Vf of the XM-L at that current? (different for each led!)
- What is the V of the battery at that current?
Vf of the XM-L will be around 3.5v
Now, allmost every battery large enough can easily deliver 3.0A @ 3.5v, so the voltage will be higher and thus the delivered current, which will result in one of these two outcomes:
- It will settle at an equilibrium, with the Vf of the led is the same as the battery.
- It will kill the LED, due to excessive current and thermal runaway (the led's Vf drops when they get warmer!).
The most fail-safe way of powering an XM-L, is using a 7135 based driver (8x for 2.8A). This will limit the current. You can use a 4.2v battery on a 3.3v led without any problem.